When you find this cache, you will be standing on top of a 65,000,000 L CSO tank. CSO means Combined Sewer Overflow. In this area, storm sewers and sanitary sewers are combined. Meaning toilet water and rainwater is piped to the waster water treatment plant. but during heavy rains, too much water enters the system and it is overloaded. Somethings gotta give, and combined soup of rainwater and raw sewage gets diverted into the nearest watercourse - in this case, Red Hill Creek. How disgusting. So this tank (actual there's two located in this area) was built to capture that water and allow it to be retained until it can be sent to the waste water treatment plant for treatment. Much better. Now the Red Hill Creek is not a toilet.

You'll noticed they landscaped quite nicely on top of the tank - two large baseball diamonds, trees, grass...you;d hardly even know you were standing on a giant tank. Except for all those utility access covers. And, the occasional foul odour. It's not a think tank, it's a stink tank.